Bengali, as an Indo-Aryan language, developed out of the same common dialects (or prakrits) that diverged from Sanskrit in the 11th through 13th centuries CE. The corrupted grammar that emerged in Magadha (what is now a great deal of eastern India) is evident in the Charyapada, a set of Buddhist texts that is partially intelligible to the speakers of, and thus indicative of the diversions in, the three groups which the "meaningless sounds" split into–the Bengali and Assamese group, the Oriya group, and the Bihari group.

Upon the Muslim conquests of India, a great deal of Arabic and Persian vocabulary entered the language, which didn't stop Chaitanya and Chandidas from promoting Hinduism and composing poems in a highly Sanskritized manner.